The invention relates to a stapling apparatus for stapling sheets arranged in stacks, with a stapling head which drives the staples in from the one side, and with a counterbearing, associated with the other side, on which a clinching apparatus which clinches the ends of the staples is arranged; the stapling apparatus having a slider that can be moved by a drive apparatus having a radial cam, and that controls raising or adjustment of the counterbearing.
In a stapling apparatus of this kind disclosed by U.S. patent application Ser. No. 5,141,143, before the stapling operation the counterbearing is directed from above toward the sheet stack being stapled, but initially is not in contact with it. The operation of driving in the staple, occurring from the underside, occurs with interposition of a compression spring. During the driving operation the sheet stack is raised and laid against the counterbearing, the compression spring effecting compensation for the thickness of the sheet stack. Because the sheet stack being stapled is raised prior to the stapling operation, its position can shift, so that precisely aligned guidance of the staple during the stapling operation is not guaranteed. In addition, the known stapling apparatus requires a comparatively high drive torque and thus high drive motor output, since the compression spring, designed to transfer the maximum driving-in force, must be compressed at each thickness compensation operation.